Buffer Layers And Interlayers That Promote BiSbx (012) Alloy Orientation For SOT And MRAM Devices

ABSTRACT

The present disclosure generally relate to spin-orbit torque (SOT) magnetic tunnel junction (MTJ) devices comprising a buffer layer, a bismuth antimony (BiSb) layer having a (012) orientation disposed on the buffer layer, and an interlayer disposed on the BiSb layer. The buffer layer and the interlayer may each independently be a single layer of material or a multilayer of material. The buffer layer and the interlayer each comprise at least one of a covalently bonded amorphous material, a tetragonal (001) material, a tetragonal (110) material, a body-centered cubic (bcc) (100) material, a face-centered cubic (fcc) (100) material, a textured bcc (100) material, a textured fcc (100) material, a textured (100) material, or an amorphous metallic material. The buffer layer and the interlayer inhibit antimony (Sb) migration within the BiSb layer and enhance uniformity of the BiSb layer while further promoting the (012) orientation of the BiSb layer.

FIELD OF THE DISCLOSURE

Embodiments of the present disclosure generally relate to a buffer layerand an interlayer that inhibit antimony (Sb) migration within a bismuthantimony (BiSb) layer having a (012) orientation.

DESCRIPTION OF THE RELATED ART

BiSb is a material that has been proposed as a spin Hall layer for spintorque oscillator (STO) and magnetoresistive random access memory (MRAM)devices. BiSb is a narrow gap topological insulator with both giant spinHall effect and high electrical conductivity.

N. H. D. Khang, Y. Ueda, and P. N. Hai, “A conductive topologicalinsulator with large spin Hall effect for ultralow power spin-orbittorque switching,” Nature Materials, v. 17, 808 (2018), discovered thatBiSb with a (012) crystallographic orientation has a high spin Hallangle and high conductivity in comparison to BiSb with a (001)crystallographic orientation. BiSb with a (012) crystallographicorientation was formed on a MnGa film with a (001) crystallographicorientation which was formed on a GaAs substrate with a (001)crystallographic orientation.

N. Roschewsky, E. S. Walker, P. Gowtham, S. Muschinske, F. Hellman, S.R. Bank, and S. Salahuddin, “Spin-orbit torque and Nernst effect inBi—Sb/Co heterostructures”, Phys. Rev. B, vol. 99, 195103 (2 May 2019),recognized that BiSb growth, crystallographic orientation, spin Hallangle, and high conductivity had poor consistency among experiments.

E. S. Walker, S. Muschinske, C. J. Brennan, S. R. Na, T. Trivedi, S. D.March, Y. Sun, T. Yang, A. Yau, D. Jung, A. F. Briggs, E. M. Krivoy, M.L. Lee, K. M. Liechti, E. T. Yu, D. Akinwande, and S. R. Bank,“Composition-dependent structural transition in epitaxial Bi1-xSbx thinfilms on Si (111)”, Phys. Rev. Materials 3, 064201 (7 Jun. 2019),established growing Bi1-xSbx thin films at any thickness (including veryultra-thin films) on Si(111) substrates but only for concentrations inthe 9% to 28% Sb concentration range, which happen to overlap the rangeneeded to exhibit TI (Topological Insulator) properties. Furthermore,ultra-thin <20 Å Bi films could be grown with a strong (012)orientation, suggesting ultra-thin Bi/BiSb film laminates could be grownexpitaxially with strong (012) orientation.

FIG. 11 illustrates a TEM-EELS line scan of relative Sb concentration ina 100 Å thick BiSb layer within a SOT stack without proper adjacentbuffer and interlayers. FIG. 11 shows the problem of Sb migration to theinterfaces from the bulk which could be improved with the use ofultra-thin Bi layers of thickness t, 0<t<10 Å, sandwiching BiSb SOTlayers that can serve as Sb composition modulations layers, to helpimprove the chemical uniformity and maintain (012) texture and structureof the BiSb layer degraded by Sb migration. However, both thin Bi andBiSb film adhesion of the BiSb layer with a (012) orientation on Si(111) was poor.

Therefore, there is a need for an improved process to form BiSb withhigh spin Hall angle and high conductivity and for improved deviceshaving a BiSb layer with high spin Hall angle and high conductivity.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relate to spin-orbit torque (SOT)magnetic tunnel junction (MTJ) devices comprising a buffer layer, abismuth antimony (BiSb) layer having a (012) orientation disposed on thebuffer layer, and an interlayer disposed on the BiSb layer. The bufferlayer and the interlayer may each independently be a single layer ofmaterial or a multilayer of material. The buffer layer and theinterlayer each comprise at least one of a covalently bonded amorphousmaterial, a tetragonal (001) material, a tetragonal (110) material, abody-centered cubic (bcc) (100) material, a face-centered cubic (fcc)(100) material, a textured bcc (100) material, a textured fcc (100)material, a textured (100) material, or an amorphous metallic material.The buffer layer and the interlayer inhibit antimony (Sb) migrationwithin the BiSb layer and enhance uniformity of the BiSb layer whilefurther promoting the (012) orientation of the BiSb layer.

In one embodiment, a spin-orbit torque (SOT) magnetic tunnel junction(MTJ) device comprises a substrate, a buffer layer formed over thesubstrate, the buffer layer comprising: an amorphous layer comprising amaterial in an amorphous structure, wherein the material comprises acovalently bonded carbide, a covalently bonded oxide, or a covalentlybonded nitride, and a bismuth antimony (BiSb) layer formed over thebuffer layer, the BiSb layer having a (012) orientation, wherein thebuffer layer is configured to reduce migration of Sb in the BiSb layer.

In another embodiment, a SOT MTJ device comprises a substrate, a bufferlayer formed on the substrate, the buffer layer comprising: at least onefirst intermediary layer, the at least one first intermediary layercomprising at least one of: a tetragonal (001) material, a tetragonal(110) material, a body-centered cubic (bcc) (100) material, aface-centered cubic (fcc) (100) material, a textured bcc (100) material,a textured fcc (100) material, a textured (100) material, or anamorphous material comprising a covalently bonded carbide, a covalentlybonded oxide, or a covalently bonded nitride, and a bismuth antimony(BiSb) layer stack formed over the buffer layer comprising a BiSb layerhaving a (012) orientation, wherein the BiSb layer stack furthercomprises: a first Bi layer, wherein the BiSb layer is disposed on thefirst Bi layer, and a second Bi layer disposed on the BiSb layer,wherein the first and second Bi layers: each has a thickness greaterthan about 0 Å and less than about 10 Å, and sandwich the BiSb layer topromote a (012) BiSb texture and serve as Sb composition modulationslayers configured to improve a chemical uniformity and structure of theBiSb layer degraded by Sb migration.

In yet another embodiment, a SOT MTJ device comprises a substrate and abuffer layer formed over the substrate, the buffer layer comprising: atextured layer with a (100) orientation and a first intermediary layerdisposed over the textured layer, the first intermediary layercomprising at least one of a cubic crystal structure selected from thegroup consisting of tetragonal (001), tetragonal (110), body-centeredcubic (bcc) (100), face-centered cubic (fcc) (100), textured bcc (100),and textured fcc (100). The SOT MTJ device further comprises a bismuthantimony (BiSb) layer formed over the buffer layer, the BiSb layerhaving a (012) orientation, wherein the buffer layer is configured toreduce diffusion of Sb in the BiSb layer, and an interlayer disposed onthe BiSb layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a schematic illustration of certain embodiments of a magneticmedia drive including a MAMR write head having a SOT MTJ device.

FIG. 2 is a fragmented, cross-sectional side view of certain embodimentsof a read/write head having a SOT MTJ device.

FIGS. 3A-3B illustrate spin-orbit torque (SOT) magnetic tunnel junction(MTJ) devices, according to various embodiments.

FIGS. 4A-4D illustrate exemplary multilayer structures of the bufferlayer and/or the interlayer that may be utilized with the SOT MTJdevices of FIGS. 3A-3B, according to various embodiments.

FIG. 5 is a schematic cross-sectional view of a BiSb layer comprisingsublayers, which may be the BiSb layer of the SOT MTJ devices of FIGS.3A-3B, according to one embodiment.

FIGS. 6A-6E are schematic views illustrating atom lattice structures oflayers within the SOT MTJ devices of FIGS. 3A-3B, according to variousembodiments.

FIGS. 7-8 are graphs of a textured layer of 30 Å of RuAl in a B2 phasethat is disposed on an amorphous layer of 30 Å of NiFeTa, in which a(100) fcc textured layer (MgO), a (100) bcc textured layers (Cr, Ta, W,W/Ta), and (100) B2 texture layer (NiAl) are grown on.

FIG. 9A is a schematic cross-sectional view of a SOT device for use in aMAMR write head, such as the MAMR write head of the drive of FIG. 1 orother suitable magnetic media drives.

FIGS. 9B-9C are schematic MFS views of certain embodiments of a portionof a MAMR write head with a SOT device of FIG. 9A.

FIG. 10 is a schematic cross-sectional view of a SOT MTJ used as a MRAMdevice.

FIG. 11 shows the problem of Sb migration to the interfaces from thebulk BiSb layer, according to one embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

In the following, reference is made to embodiments of the disclosure.However, it should be understood that the disclosure is not limited tospecific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practice thedisclosure. Furthermore, although embodiments of the disclosure mayachieve advantages over other possible solutions and/or over the priorart, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the disclosure. Thus, the followingaspects, features, embodiments and advantages are merely illustrativeand are not considered elements or limitations of the appended claimsexcept where explicitly recited in a claim(s). Likewise, reference to“the disclosure” shall not be construed as a generalization of anyinventive subject matter disclosed herein and shall not be considered tobe an element or limitation of the appended claims except whereexplicitly recited in a claim(s).

The present disclosure generally relate to spin-orbit torque (SOT)magnetic tunnel junction (MTJ) devices comprising a buffer layer, abismuth antimony (BiSb) layer having a (012) orientation disposed on thebuffer layer, and an interlayer disposed on the BiSb layer. The bufferlayer and the interlayer may each independently be a single layer ofmaterial or a multilayer of material. The buffer layer and theinterlayer each comprise at least one of a covalently bonded amorphousmaterial, a tetragonal (001) material, a tetragonal (110) material, abody-centered cubic (bcc) (100) material, a face-centered cubic (fcc)(100) material, a textured bcc (100) material, a textured fcc (100)material, a textured (100) material, or an amorphous metallic material.The buffer layer and the interlayer inhibit antimony (Sb) migrationwithin the BiSb layer and enhance uniformity of the BiSb layer whilefurther promoting the (012) orientation of the BiSb layer.

Embodiments of the present disclosure generally relate to a buffer layerthat promotes preservation of a bismuth antimony (BiSb) layer having a(012) orientation. Antimony (Sb) is highly reactive, and the bufferlayer provides a low-reactive medium that reduces chemical interactionbetween the BiSb layer and external materials while promoting the growthof the BiSb in a (012) orientation. The configuration of the bufferlayer reduces the migration of Sb in the BiSb layer.

A BiSb layer having a (012) orientation has a large spin Hall angleeffect and high electrical conductivity. A BiSb layer having a (012)orientation can be used to form a spin-orbit torque (SOT) magnetictunnel junction (MTJ) device. For example, a BiSb layer having a (012)orientation can be used as a spin Hall layer in a spin-orbit torquedevice in a magnetic recording head, e.g., as part of a read head,and/or a microwave assisted magnetic recording (MAMR) write head. Inanother example, a BiSb layer having a (012) orientation can be used asa spin Hall electrode layer in a magnetoresistive random access memory(MRAM) device. The SOT MTJ device can be in a perpendicular stackconfiguration or an in-plane stack configuration. The SOT MTJ device canbe utilized in, for example, MAMR writing heads, in MRAM, in artificialintelligence chips, and in other applications. A BiSb layer stack 304with a (012) orientation has a higher spin Hall angle and higherperformance in a SOT MTJ device than a BiSb layer with a (001)orientation.

FIG. 1 is a schematic illustration of certain embodiments of a magneticmedia drive 100 including a MAMR write head having a SOT MTJ device.Such a magnetic media drive may be a single drive or comprise multipledrives. For the sake of illustration, a single disk drive 100 is shownaccording to certain embodiments. As shown, at least one rotatablemagnetic disk 112 is supported on a spindle 114 and rotated by a drivemotor 118. The magnetic recording on each magnetic disk 112 is in theform of any suitable patterns of data tracks, such as annular patternsof concentric data tracks (not shown) on the magnetic disk 112.

At least one slider 113 is positioned near the magnetic disk 112, eachslider 113 supporting one or more magnetic head assemblies 121 thatinclude a SOT device. As the magnetic disk 112 rotates, the slider 113moves radially in and out over the disk surface 122 so that the magnetichead assembly 121 may access different tracks of the magnetic disk 112where desired data are written. Each slider 113 is attached to anactuator arm 119 by way of a suspension 115. The suspension 115 providesa slight spring force which biases the slider 113 toward the disksurface 122. Each actuator arm 119 is attached to an actuator means 127.The actuator means 127 as shown in FIG. 2 may be a voice coil motor(VCM). The VCM includes a coil movable within a fixed magnetic field,the direction and speed of the coil movements being controlled by themotor current signals supplied by control unit 129.

During operation of the disk drive 100, the rotation of the magneticdisk 112 generates an air bearing between the slider 113 and the disksurface 122 which exerts an upward force or lift on the slider 113. Theair bearing thus counter-balances the slight spring force of suspension115 and supports slider 113 off and slightly above the disk surface 122by a small, substantially constant spacing during normal operation.

The various components of the disk drive 100 are controlled in operationby control signals generated by control unit 129, such as access controlsignals and internal clock signals. Typically, the control unit 129comprises logic control circuits, storage means and a microprocessor.The control unit 129 generates control signals to control various systemoperations such as drive motor control signals on line 123 and headposition and seek control signals on line 128. The control signals online 128 provide the desired current profiles to optimally move andposition slider 113 to the desired data track on disk 112. Write andread signals are communicated to and from write and read heads on theassembly 121 by way of recording channel 125.

The above description of a typical magnetic media drive and theaccompanying illustration of FIG. 1 are for representation purposesonly. It should be apparent that magnetic media drives may contain alarge number of media, or disks, and actuators, and each actuator maysupport a number of sliders.

FIG. 2 is a fragmented, cross-sectional side view of certain embodimentsof a read/write head 200 having a SOT MTJ device. The read/write head200 faces a magnetic media 112. The read/write head 200 may correspondto the magnetic head assembly 121 described in FIG. 1 . The read/writehead 200 includes a media facing surface (MFS) 212, such as a gasbearing surface, facing the disk 112, a MAMR write head 210, and amagnetic read head 211. As shown in FIG. 2 , the magnetic media 112moves past the MAMR write head 210 in the direction indicated by thearrow 232 and the read/write head 200 moves in the direction indicatedby the arrow 234.

In some embodiments, the magnetic read head 211 is a magnetoresistive(MR) read head that includes an MR sensing element 204 located betweenMR shields 51 and S2. In other embodiments, the magnetic read head 211is a magnetic tunnel junction (MTJ) read head that includes a MTJsensing device 204 located between MR shields 51 and S2. The magneticfields of the adjacent magnetized regions in the magnetic disk 112 aredetectable by the MR (or MTJ) sensing element 204 as the recorded bits.The SOT MTJ device of various embodiments can be incorporated into theread head 211.

The MAMR write head 210 includes a main pole 220, a leading shield 206,a trailing shield 240, a spin orbital torque (SOT) device 250, and acoil 218 that excites the main pole 220. The coil 218 may have a“pancake” structure which winds around a back-contact between the mainpole 220 and the trailing shield 240, instead of a “helical” structureshown in FIG. 2 . The SOT device 250 is formed in a gap 254 between themain pole 220 and the trailing shield 240. The main pole 220 includes atrailing taper 242 and a leading taper 244. The trailing taper 242extends from a location recessed from the MFS 212 to the MFS 212. Theleading taper 244 extends from a location recessed from the MFS 212 tothe MFS 212. The trailing taper 242 and the leading taper 244 may havethe same degree of taper, and the degree of taper is measured withrespect to a longitudinal axis 260 of the main pole 220. In someembodiments, the main pole 220 does not include the trailing taper 242and the leading taper 244. Instead, the main pole 220 includes atrailing side (not shown) and a leading side (not shown), and thetrailing side and the leading side are substantially parallel. The mainpole 220 may be a magnetic material, such as a FeCo alloy. The leadingshield 206 and the trailing shield 240 may be a magnetic material, suchas a NiFe alloy. In certain embodiments, the trailing shield 240 caninclude a trailing shield hot seed layer 241. The trailing shield hotseed layer 241 can include a high moment sputter material, such as CoFeNor FeXN, where X includes at least one of Rh, Al, Ta, Zr, and Ti. Incertain embodiments, the trailing shield 240 does not include a trailingshield hot seed layer.

FIGS. 3A-3B illustrate spin-orbit torque (SOT) magnetic tunnel junction(MTJ) devices 300, 301, according to various embodiments. The SOT MTJdevices 300, 301 may each individually be used in the MAMR write head ofthe drive 100 of FIG. 1 , the read/write head 200 of FIG. 2 , or othersuitable magnetic media drives.

FIG. 3A illustrates a SOT MTJ device 300, according to one embodiment.The SOT MTJ device 300 comprises a substrate 302, a buffer layer 310disposed on the substrate 302, a BiSb layer 304 or BiSb layer stack 304comprising with a crystal orientation of (012) disposed on the bufferlayer 310, an interlayer 320 disposed on the BiSb layer 304, a tunnelmagnetoresistance (TMR)-like free layer 322 disposed on the interlayer320, and a MgO layer 324 disposed on the TMR-like free layer 322. FIG.3B illustrates a reverse SOT MTJ device 301, according to oneembodiment. The SOT MTJ device 301 comprises the substrate 302, a MgOlayer 324 disposed on the substrate 302, a TMR-like free layer 322disposed on the MgO layer 324, the buffer layer 310 disposed on theTMR-like free layer 322, the BiSb layer 304 comprising with a crystalorientation of (012) disposed on the buffer layer 310, and theinterlayer 320 disposed on the BiSb layer 304. The SOT MTJ devices 300,301 comprise the same layers 302, 304, 310, 320, 322, 324 in differentarrangements.

The substrate 302 can be a silicon substrate or an alumina substrate.The silicon substrate 302 has a cubic structure of (111), (100), (100),or other crystal orientations. The alumina substrate 302 has a hexagonalstructure with (001) orientations or with other crystal orientations orhas an amorphous structure. The substrate 302 can be a bare substrate orcan have one or more layers formed thereover, such as an oxide layerthermally grown or deposited thereover.

In one embodiment, the interlayer 320 may be the same material as thebuffer layer 310. For example, like shown in FIGS. 3A-3B, the interlayer320 and the buffer layer 310 may each individually comprise a singlelayer of a crystalline or amorphous material. In another example, theinterlayer 320 and the buffer layer 310 may each individually comprisemultiple layers of crystalline and/or amorphous materials. In anotherembodiment, the interlayer 320 and the buffer layer 310 eachindividually comprise one or more different materials.

The buffer layer 310 and the interlayer 320 may each individually be amultilayer structure, as discussed further below in FIGS. 4A-4D. In oneembodiment, the buffer layer 310 and/or the interlayer 320 is acovalently bonded amorphous layer. The covalently bonded amorphousmaterial may comprise one of a covalently bonded carbide, a covalentlybonded oxide, or a covalently bonded nitride. The covalently bondedamorphous material has a lattice constant of the crystal structure(afcc) between about 3.5 Å and 3.71 Å, and the covalently bondedamorphous material has a nearest neighbor distance equal to about afccdivided by the square root of 3. In some configurations, the nearestneighbor distance is between about 2.0 Å to about 2.2 Å.

In some embodiments, the buffer layer 310 and the interlayer 320 eachindividually comprises one or more highly bonded materials such that thematerials are less likely to interact with Sb or Bi in the BiSb layer304 than ionic chemicals. As further discussed below in FIGS. 4A-4D, thebuffer layer 310 and the interlayer 320 may each individually compriseone or more materials selected from the group consisting of: acovalently bonded amorphous material, a tetragonal (001) material, atetragonal (110) material, a body-centered cubic (bcc) (100) material, aface-centered cubic (fcc) (100) material, a textured bcc (100) material,a textured fcc (100) material, a textured (100) material, an amorphousmetallic material, and a layered combination of one or more of any ofthe preceding materials.

FIGS. 4A-4D illustrate exemplary multilayer structures of the bufferlayer 310 and/or the interlayer 320 that may be utilized with the SOTMTJ devices 300, 301 of FIGS. 3A-3B, according to various embodiments.As shown in FIGS. 4A-4D, the buffer layer 310 and the interlayer 320 mayeach individually comprise one or more amorphous or crystallinesublayers or intermediate layers 312, 314, 316, 318, and 326.

The embodiments of FIGS. 4A-4D can be used in combination with eachother and are not an exclusive list of possible buffer layers 310 and/orinterlayers 320. Moreover, while each of FIGS. 4A-4D describes both thebuffer layer 310 and the interlayer 320, the buffer layer 310 and theinterlayer 320 may have different configurations or a different amountof sublayers or intermediate layers 312, 314, 316, 318, and 326.Furthermore, the buffer layer 310 may be the single layer of acrystalline or amorphous material as discussed and shown above in FIGS.3A-3B and the interlayer 320 may be a multilayer structure as describedbelow in FIGS. 4A-4D, or vice versa.

In FIG. 4A, the buffer layer 310 and/or the interlayer 320 comprises afirst intermediate layer 312 and a second intermediate layer 314disposed on the first intermediate layer 312. In one embodiment, thefirst intermediate layer 312 comprises a metallic amorphous material andthe second intermediate layer 314 comprises a tetragonal (001) or (110)material. In another embodiment, the first intermediate layer 312comprises a metallic amorphous material and the second intermediatelayer 314 comprises a textured (100) layer.

The tetragonal (001) or (110) material may have an a-axis in the rangeof about 4.49 Å to about 4.69 Å and a c-axis in the range of about 2.88Å to about 3.15 Å. The tetragonal (001) or (110) material may have ana-axis lattice parameter in the range of about 4.20 Å to about 4.75 Å.The tetragonal (001) or (110) material may be selected from the groupconsisting of: SbO₂, TiO₂, IrO₂, RuO₂, CrO₂, VO₂, OsO₂, RhO₂, PdO₂,WVO₄, CrNbO₄, SnO₂, GeO₂, and composites thereof with one or moreelements selected from the group consisting of: W, Ta, and Nb.

The amorphous metallic material may be selected from the groupconsisting of: NiTa, NiFeTa, NiNb, NiW, NiFeW, NiFeHf, CoHfB, CoZrTa,CoFeB, NiFeB, CoB, FeB, and alloy combinations thereof with one or moreelements selected from the group consisting of: Ni, Fe, Co, Zr, W, Ta,Hf, Ag, Pt, Pd, Si, Ge, Mn, Al, and Ti.

The textured (100) layer may be selected from the group consisting of:(1) RuAl, (2) Cr incorporated according to several options: (2a)deposited at a temperature greater than or equal to 250° C., (2b) inheated CrX alloys where X=Ru, Mo, W, or Ti<10 at. %, or CrMo_(n) where nis about 20 at. % to about 50 at. %, (2c) in a stack of heated (e.g., toless than or equal to about 200° C.) Cr/CrMo_(n) orCrMo_(n)/Cr/CrMo_(n).

In FIG. 4B, the buffer layer 310 and/or the interlayer 320 comprises afirst intermediate layer 312, a second intermediate layer 314 disposedon the first intermediate layer 312, and a third intermediate layer 316disposed on the second intermediate layer 314. The first intermediatelayer 312 comprises a metallic amorphous material and the secondintermediate layer 314 comprises a textured (100) layer. In oneembodiment, the third intermediate layer 316 comprises a textured bcc(100) layer. In another embodiment, the third intermediate layer 316comprises an fcc (100) layer. In yet another embodiment, the thirdintermediate layer 316 comprises a tetragonal (001) layer.

The bcc (100) material may selected from the group consisting of: V, Nb,Mo, W, Ta, WTi₅₀, Al₁₀Nb₄₀Ti₅₀, Cr, RuAl in a B2 phase, NiAl in a B2phase, RhAl in a B2 phase, and alloy combinations thereof with one ormore elements selected from the group consisting of: Ti, Al, Pd, Pt, Ni,Fe, and Cr.

The fcc (100) material may have a lattice parameter in the range ofabout 4.20 Å to about 4.70 Å. The fcc (100) material may be selectedfrom the group consisting of oxides, carbides, and nitrides of: (1) FeO,CoO, NiO, ZrO, MgO, TiO, ScN, TiN, NbN, ZrN, HfN, TaN, ScC, TiC, NbC,ZrC, HfC, TaC, and WC; (2) zinc blend cubic fcc (100) materials selectedfrom the group consisting of: CoO, SIC, GaN, FeN, and ZnO; (3) compositecombinations of (1) and (2) thereof with one or more elements selectedfrom the group of W, Al, and Si; and (4) fcc metals selected from thegroup consisting of: MoZr₁₀, MoNi₂₀, NbZr₂₀, and alloy combinationsthereof with one or more elements selected from the group consisting of:W, Al, and Si. In other words, the fcc (100) is selected from the groupconsisting of: FeO, CoO, ZrO, MgO, TiO, ScN, TiN, NbN, ZrN, HfN, TaN,ScC, TiC, NbC, ZrC, HfC, TaC, WC, CoO, SIC, GaN, FeN, ZnO, MoZr₁₀,MoNi₂₀, NbZr₂₀, and composite combinations thereof with one or moreelements selected from the group of: W, Al, and Si.

In FIG. 4C, the buffer layer 310 and/or the interlayer 320 comprises afirst intermediate layer 312, a second intermediate layer 314 disposedon the first intermediate layer 312, a third intermediate layer 316disposed on the second intermediate layer 314, and a fourth intermediatelayer 318 disposed on the third intermediate layer 316. The firstintermediate layer 312 comprises a metallic amorphous material and thesecond intermediate layer 314 comprises a textured (100) layer. In oneembodiment, the third intermediate layer 316 comprises a textured bcc(100) layer and the fourth intermediate layer 318 comprises an fcc (100)layer.

In another embodiment, the third intermediate layer 316 comprises atextured (100) bcc material and the fourth intermediate layer 318comprises a tetragonal (110) material. In yet another embodiment, thethird intermediate layer 316 comprises a textured (100) bcc material andthe fourth intermediate layer 318 comprises a tetragonal (001) material.

In FIG. 4D, the buffer layer 310 and/or the interlayer 320 comprises afirst intermediate layer 312 that comprises a metallic amorphousmaterial, a second intermediate layer 314 that comprises a textured(100) material, a third intermediate layer 316 that comprises a textured(100) bcc material, a fourth intermediate layer 318 that comprises atetragonal (001) material, and a fifth intermediate layer 326 thatcomprises an fcc (100) material.

In certain embodiments, the buffer layer 310 and/or the interlayer 320are deposited by physical vapor deposition (PVD), such as sputtering,molecular beam epitaxy, ion beam deposition, other suitable PVDprocesses, or combinations thereof. In certain embodiments, the bufferlayer 310 and/or the interlayer 320 are deposited at ambienttemperatures, such as from 20° C. to about 25° C. In one aspect, formingthe buffer layer 310 and/or the interlayer 320 at ambient temperaturesreduces thermal migration of the intermediary layers 312, 314, 316, 318,and 326. In another aspect, forming the buffer layer 310 at ambienttemperatures minimizes altering the magnetization direction of magneticmaterials formed on substrate 302 prior to forming the buffer layer 310.

In certain embodiments, a post etch of the buffer layer 310 and/or theinterlayer 320 is conducted. For example, the buffer layer 310 and/orthe interlayer 320 can be post etched by an ion etch, such as directingargon ions to etch the intermediary layer 312, 314, 316, 318, and 326 onwhich the BiSb layer 304 is disposed. It is believed that a post etchenhances the interface between the intermediary layer 312, 314, 316,318, and 326 and the BiSb layer 304 by cleaning the surface of theintermediary layer 312, 314, 316, 318, and 326 and/or by distorting theintermediary layer 312, 314, 316, 318, and 326 to promote (012) growthof the BiSb layer 304 thereover.

By including a material that matches the BiSb (012) textured surface ofthe BiSb layer 304, such as at least one of a covalently bondedamorphous material, a tetragonal (001) material, a tetragonal (110)material, a body-centered cubic (bcc) (100) material, a face-centeredcubic (fcc) (100) material (both rock salt and zinc blend), a texturedbcc (100) material, a textured fcc (100) material, a textured (100)material, or an amorphous metallic material, in the buffer layer 310 andthe interlayer 320 disposed in contact with the BiSb layer 304, a (012)growth of the BiSb layer 304 is promoted and surface roughness of theBiSb layer 304 is reduced by reducing the overall grain size of the Biand Sb atoms of the BiSb layer 304. Improving or maintaining the BiSb(012) textured surface reduces chemical interactions with the BiSb layer304, which inhibits Sb migration of the BiSb layer 304. Furthermore,including a material that matches the BiSb (012) textured surface of theBiSb layer 304 disposed in contact with the BiSb layer 304 improvesepitaxy, reduces roughness, and enhances uniformity of the BiSb layer304.

FIG. 5 is a schematic cross-sectional view of a BiSb layer stack 304comprising sublayers, which may be the BiSb layer stack 304 of the SOTMTJ devices 300, 301 of FIGS. 3A-3B, according to one embodiment. TheBiSb layer stack 304 comprises Bi laminates 304 a, 304 c. A first Bilaminate 304 a is disposed on the buffer layer 310. A BiSb layer 304 bis disposed on the first Bi laminate 304 a. The BiSb layer 304 b maycomprise Sb in an atomic percentage of about 10% to about 20%. A secondBi laminate 304 c is disposed on the BiSb layer 304 b. In someembodiments, the first and second Bi laminates 304 a, 304 c each has athickness of about 0 Å to about 10 Å.

The BiSb layer stack 304 has a (012) orientation. In some embodiments,the BiSb layer stack 304 comprises Bi1-xSbx wherein x is 0<x<1. Incertain embodiments, the BiSb layer stack 304 comprises Bi1-xSbx whereinx is 0.05<x<0.22 or comprises antimony in an atomic percent content fromabout 7% to about 22%. The BiSb layer stack 304 has a thickness of about20 Å to about 200 Å, such as about 50 Å to about 150 Å.

TABLE 1 shows one example of the properties of a BiSb layer stack 304with a (012) orientation in comparison to beta-tantalum and a BiSb layerwith a (001) orientation.

TABLE 1 Spin Hall conductivity Power angle θ_(SH) σ (10⁶ Ω⁻¹m⁻¹)(relative) Beta-Ta −0.15 0.52 1 BiSb (001) 11 0.25 3.9 × 10⁻⁰⁴ BiSb(012) 52 0.25 1.7 × 10⁻⁰⁵

A BiSb layer stack 304 with a (012) orientation has similar electricalconductivity to the beta-tantalum (Beta-Ta) and a much larger spin Hallangle than Beta-Ta or a BiSb layer with a (001) orientation. Therefore,the relative power to produce a spin Hall effect is lower for BiSb (012)in comparison to Beta-Ta or BiSb (001).

FIGS. 6A-6E are schematic views illustrating atom lattice structures oflayers within the SOT MTJ devices 300, 301 of FIGS. 3A-3B, according tovarious embodiments. The various atoms in each of FIG. 6A-6E arerepresented by dots.

As shown in FIG. 6A, a BiSb layer 304 or a BiSb layer stack 304 with a(012) orientation has a rectangular surface with dimensions of a=about4.54 Å and b=about 4.75 Å with about 3% mismatch in one direction. Eventhough the crystalline lattice structure of the BiSb layer or layerstack 304 is rectangular, it can be approximated as a square latticewere a=4.64 Å. When the buffer layer 310 and/or the interlayer 320 aremade of material with a lattice structure or a nearest neighbor distancenear 4.64 Å, the buffer layer 310 material and/or the interlayer 320material can also be used to promote the growth of BiSb in a (012)orientation.

FIG. 6B illustrates a comparison of the crystalline configuration of fccand bcc lattice structures. The filled dots represent bcc atoms and theopen dots represent fcc atoms. As shown in FIG. 6B, the a_(fcc) equal toa_(bcc)√2. Thus, both the crystalline configurations of fcc and bcclattice structures can be approximated as square lattices.

FIG. 6C is an exemplary orthogonal view illustrating the tetragonalstructure of RuO₂ in a (001) orientation, where the filled in dotsrepresent Ru and the open dots represent O. RuO₂ is one example of atetragonal crystal lattice structure in a (001) orientation that may beutilized in the buffer layer 310 and/or the interlayer 320. However, oneskilled in the art would know that other chemicals with a tetragonal(001) orientation may be utilized instead, and the tetragonal (001)orientation is not intended to be limited to RuO₂. For RuO₂, therectangular prismatic dimensions are a=4.50 Å, b=4.50 Å, and c=3.10 Å.Therefore, RuO₂ has a 2D square lattice structure where a=4.50 Å.Compared to the crystal lattice structure of BiSb, where a=4.64 Å, thereis a 3% difference. Therefore, RuO₂ with an (001) orientation can beutilized to grow BiSb in a (012) texture.

FIG. 6D is a schematic plan view illustrating the tetragonal structureof RuO₂ in a (110) orientation. FIG. 6E illustrates a comparison of thecrystalline configuration of MgO in an fcc (100) orientation and RuO₂ ina tetragonal (110) orientation. For RuO₂ with a (110) orientation, RuO₂has a crystal lattice structure where a=6.36 Å and b=3.10 Å. As seen inthe dashed square in FIG. 6D, there is a larger mismatch between BiSband RuO₂ in a tetragonal (110) orientation due to the Ru—Ru and Ru—Obond length differences. There is a 37% mismatch between the BiSb avalue and the RuO₂ a value, and a 33% mismatch between the BiSb a valueand the RuO₂ b value. However, as seen in FIGS. 6D-6E, the distancesbetween the oxygen atoms (represented by the open dots) matches withBiSb in a (012) orientation.

FIGS. 7 and 8 are graphs 700, 800 of a textured layer of about 30 Å ofRuAl in a B2 phase that is disposed on an amorphous layer of about 30 Åof NiFeTa. In FIG. 7 , the graph 700 shows that this layeringconfiguration with a close lattice match results in a uniformcrystalline lattice structure. A tenuous lattice match results in someof the material forming a crystal lattice structure that is differentfrom the bulk of the material. In FIG. 7 , either MgO or Ta is disposedon the RuAl layer. RuAl in the B2 phase has an a_(bcc) of 3.000 Å, andTa has an a_(bcc) of 3.306 Å, which is more than a 10% difference invalue. Due to this poor lattice match, some of the Ta forms in a (110)orientation and the rest forms in a (200) orientation. In contrast, thea√2 value for RuAl in the B2 phase is 4.243 Å and the a_(fcc) of MgO is4.210 Å. Since these values are close, the majority of the MgO forms ina (100) orientation.

Other fcc materials similar to MgO have conductive properties.Therefore, the fcc materials will reduce the shunting, improve theepitaxy, and improve the growth of the BiSb. A number of the tetragonaloxides are also conductive with high resistivities, contributing thesimilar improved growth properties as the fcc materials.

In FIG. 8 , the graph 800 shows that layering of the materials to have acloser lattice structure results in a more uniform crystalline latticestructure growth for the BiSb layer or layer stack 304. In FIG. 8 , 10 Åof W is layered on the RuAl layer, and 30 Å of Ta is layered on the Wlayer. RuAl in the B2 phase has an a_(bcc) of 3.000 Å, W has an a_(bcc)of 3.165 Å, and Ta has an a_(bcc) of 3.306 Å. Since the difference ina_(bcc) between each layer is less than 10%, the crystalline latticestructure is more uniform than the lattice structure formed with morethan a 10% difference. The Ta (100) texture is improved by using Was astrain buffer layer. Other B2 materials with lattices close to RuAl canalso be grown with a (100) texture (like NiAl, for example).

FIG. 9A is a schematic cross-sectional view of a SOT device 900 for usein a MAMR write head, such as the MAMR write head of the drive 100 ofFIG. 1 or other suitable magnetic media drives. The SOT device 900comprises a BiSb layer 304 with a (012) orientation formed over a bufferlayer 310 formed over a substrate 302, such as the BiSb layer 304 andthe buffer layer 310 of FIGS. 3A-5 . A spin torque layer (STL) 970 isformed over the BiSb layer 304. The STL 970 comprises a ferromagneticmaterial such as one or more layers of CoFe, Coir, NiFe, and CoFeX alloywherein X=B, Ta, Re, or Ir.

In certain embodiments, an electrical current shunt block layer 960 isdisposed between the BiSb layer 304 and the STL 970. The electricalcurrent shunt blocking layer 960 reduces electrical current from flowingfrom the BiSb layer 304 to the STL 970 but allows spin orbital couplingof the BiSb layer 304 and the STL 970. In certain embodiments, theelectrical current shunt blocking layer 960 comprises a magneticmaterial which provides greater spin orbital coupling between the BiSblayer 304 and the STL 970 than a non-magnetic material. In certainembodiments, the electrical current shunt blocking layer 960 comprises amagnetic material of FeCo, FeCoM, FeCoMO, FeCoMMeO, FeCoM/MeO stack,FeCoMNiMnMgZnFeO, FeCoM/NiMnMgZnFeO stack, multiple layers/stacksthereof, or combinations thereof in which M is one or more of B, Si, P,Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf,Zr, Nb, Ti, Ta, Mg, Y, or Cr. In certain embodiments, the electricalcurrent shunt blocking layer 960 is formed to a thickness from about 10Å to about 100 Å. In certain aspects, an electrical current shuntblocking layer 960 having a thickness of over 100 Å may reduce spinorbital coupling of the BiSb layer 304 and the STL 970. In certainaspects, an electrical current shunt blocking layer having a thicknessof less than 10 Å may not sufficiently reduce electrical current fromBiSb layer 304 to the STL 970.

In certain embodiments, additional layers are formed over the STL 970such as a spacer layer 980 and a pinning layer 990. The pinning layer990 can partially pin the STL 970. The pinning layer 990 comprises asingle or multiple layers of PtMn, NiMn, IrMn, IrMnCr, CrMnPt, FeMn,other antiferromagnetic materials, or combinations thereof. The spacerlayer 980 comprises single or multiple layers of magnesium oxide,aluminum oxide, other non-magnetic materials, or combinations thereof.

FIGS. 9B-9C are schematic MFS views of certain embodiments of a portionof a MAMR write head 210 with a SOT device 900 of FIG. 9A. The MAMRwrite head 210 can be the write head FIG. 2 or other suitable writeheads in the drive 100 of FIG. 1 or other suitable magnetic media drivessuch as tape drives. The MAMR write head 210 includes a main pole 220and a trailing shield 240 in a track direction. The SOT device 900 isdisposed in a gap between the main pole and the trailing shield 240.

During operation, charge current through a BiSb layer or layer stack 304acting as a spin Hall layer generates a spin current in the BiSb layer.The spin orbital coupling of the BiSb layer and a spin torque layer(STL) 970 causes switching or precession of magnetization of the STL 970by the spin orbital coupling of the spin current from the BiSb layer304. Switching or precession of the magnetization of the STL 970 cangenerate an assisting AC field to the write field. Energy assisted writeheads based on SOT have multiple times greater power efficiency incomparison to MAMR write heads based on spin transfer torque. As shownin FIG. 9B, an easy axis of a magnetization direction of the STL 970 isperpendicular to the MFS from shape anisotropy of the STL 970, from thepinning layer 990 of FIG. 9A, and/or from hard bias elements proximatethe STL 970. As shown in FIG. 9C, an easy axis of a magnetizationdirection of the STL 970 is parallel to the MFS from shape anisotropy ofthe STL 970, from the pinning layer 990 of FIG. 9A, and/or from hardbias elements proximate the STL 970.

FIG. 10 is a schematic cross-sectional view of a SOT MTJ 1001 used as aMRAM device 1000. The MRAM device 1000 comprises a reference layer (RL)1010, a spacer layer 1020 over the RL 1010, a recording layer 1030 overthe spacer layer 1020, a buffer layer 310 over an electrical currentshunt block layer 1040 over the recording layer 1030, and a BiSb layeror layer stack 304 over the buffer layer 310. The BiSb layer 304 and thebuffer layer 310 may be the BiSb layer 304 and the buffer layer 310 ofFIGS. 3A-5 .

The RL 1010 comprises single or multiple layers of CoFe, otherferromagnetic materials, and combinations thereof. The spacer layer 1020comprises single or multiple layers of magnesium oxide, aluminum oxide,other dielectric materials, or combinations thereof. The recording layer1030 comprises single or multiple layers of CoFe, NiFe, otherferromagnetic materials, or combinations thereof.

As noted above, in certain embodiments, the electrical current shuntblock layer 1040 is disposed between the buffer layer 310 and therecording layer 1030. The electrical current shunt blocking layer 1040reduces electrical current from flowing from the BiSb layer 304 to therecording layer 1030 but allows spin orbital coupling of the BiSb layer304 and the recording layer 1030. For example, writing to the MRAMdevice can be enabled by the spin orbital coupling of the BiSb layer andthe recording layer 1030, which enables switching of magnetization ofthe recording layer 1030 by the spin orbital coupling of the spincurrent from the BiSb layer 304. In certain embodiments, the electricalcurrent shunt blocking layer 1040 comprises a magnetic material whichprovides greater spin orbital coupling between the BiSb layer 304 andthe recording layer 1030 than a non-magnetic material. In certainembodiments, the electrical current shunt blocking layer 1040 comprisesa magnetic material of FeCoM, FeCoMO, FeCoMMeO, FeCoM/MeO stack,FeCoMNiMnMgZnFeO, FeCoM/NiMnMgZnFeO stack, multiple layers/stacksthereof, or combinations thereof, in which M is one or more of B, Si, P,Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf,Zr, Nb, Ti, Ta, Mg, Y, or Cr.

The MRAM device 1000 of FIG. 10 may include other layers, such aspinning layers, pinning structures (e.g., a synthetic antiferromagnetic(SAF) pinned structure), electrodes, gates, and other structures. OtherMRAM devices besides the structure of FIG. 10 can be formed utilizing aBiSb layer 304 with a (012) orientation over a buffer layer 310 to forma SOT MTJ 1001.

By including a material that matches the BiSb (012) textured surface ofthe BiSb layer, such as at least one of a covalently bonded amorphousmaterial, a tetragonal (001) material, a tetragonal (110) material, abody-centered cubic (bcc) (100) material, a face-centered cubic (fcc)(100) material, a textured bcc (100) material, a textured fcc (100)material, a textured (100) material, or an amorphous metallic material,in the buffer layer and the interlayers disposed in contact with theBiSb layer, a (012) growth of the BiSb layer is promoted and surfaceroughness of the BiSb layer is reduced by reducing the overall grainsize of the Bi and Sb atoms of the BiSb layer. Improving or maintainingthe BiSb (012) textured surface reduces chemical interactions with theBiSb layer, which inhibits Sb migration of the BiSb layer. Furthermore,including a material that matches the BiSb (012) textured surface of theBiSb layer disposed in contact with the BiSb layer improves epitaxy,reduces roughness, and enhances uniformity of the BiSb layer.

In one embodiment, a spin-orbit torque (SOT) magnetic tunnel junction(MTJ) device comprises a substrate, a buffer layer formed over thesubstrate, the buffer layer comprising: an amorphous layer comprising amaterial in an amorphous structure, wherein the material comprises acovalently bonded carbide, a covalently bonded oxide, or a covalentlybonded nitride, and a bismuth antimony (BiSb) layer formed over thebuffer layer, the BiSb layer having a (012) orientation, wherein thebuffer layer is configured to reduce migration of Sb in the BiSb layer.

The buffer layer further comprises one or more sublayers, each of theone or more sublayers comprising one or more materials selected from thegroup consisting of: a tetragonal (001) material, a tetragonal (110)material, a body-centered cubic (bcc) (100) material, a face-centeredcubic (fcc) (100) material, a textured bcc (100) material, a texturedfcc (100) material, a textured (100) material, an amorphous metallicmaterial, and a layered combination of one or more of any of thepreceding materials. At least one sublayer of the one or more sublayerscomprises the bcc (100) material, the bcc (100) material being selectedfrom the group consisting of: V, Nb, Mo, W, Ta, WTi₅₀, Al₁₀Nb₄₀Ti₅₀, Cr,CrMo, CrX where X=Ti, W, Mo, Ru, or RuAl in a B2 phase, and alloycombinations thereof with elements selected from the group consistingof: Ti, Al, Pd, Pt, Ni, Fe, and Cr. At least one sublayer of the one ormore sublayers comprises the fcc (100) material, the fcc (100) materialbeing selected from the group consisting of: FeO, CoO, ZrO, MgO, TiO,ScN, TiN, NbN, ZrN, HfN, TaN, ScC, TiC, NbC, ZrC, HfC, TaC, WC, CoO,SIC, GaN, FeN, ZnO, MoZr₁₀, MoNi₂₀, NbZr₂₀, and composite combinationsthereof with one or more elements selected from the group of: W, Al, andSi.

At least one sublayer of the one or more sublayers comprises thetetragonal (001) or (110) material, the tetragonal (001) or (110)material being selected from the group consisting of: SbO₂, TiO₂, IrO₂,RuO₂, CrO₂, VO₂, OsO₂, RhO₂, PdO₂, WVO₄, CrNbO₄, SnO₂, GeO₂, compositesthereof, and with elements selected from the group consisting of: W,Taand Nb. The tetragonal (001) or (110) material has an a-axis in therange of about 4.49 Å to about 4.69 Å and a c-axis in the range of about2.88 Å to about 3.15 Å. At least one sublayer of the one or moresublayers comprises the amorphous metallic material, the amorphousmetallic material being selected from the group consisting of: NiTa,NiFeTa, NiNb, NiW, NiFeW, NiFeHf, CoHfB, CoZrTa, CoFeB, NiFeB, CoB, FeB,and alloy combinations thereof with elements selected from the groupconsisting of: Ni, Fe, Co, Zr, W, Ta, Hf, Ag, Pt, Pd, Si, Ge, Mn, Al,and Ti.

The material in the amorphous structure has a nearest neighbor XRDdiffraction peak with d-spacing equal to about 2.0 Å to about 2.2 Å,corresponding to a (111) d-spacing from a_(fcc) crystal structure wherea_(fcc) is between about 3.5 Å and 3.8 Å. The SOT MTJ device furthercomprises an interlayer disposed on the BiSb layer, the interlayercomprising one or more materials selected from the group consisting of:a tetragonal (001) material, a tetragonal (110) material, abody-centered cubic (bcc) (100) material, a face-centered cubic (fcc)(100) material, a textured bcc (100) material, a textured fcc (100)material, a textured (100) material, an amorphous material comprisingcovalently bonded carbide, oxide, or nitride, an amorphous metallicmaterial, and a layered combination of one or more of any of thepreceding materials.

In another embodiment, a SOT MTJ device comprises a substrate, a bufferlayer formed on the substrate, the buffer layer comprising: at least onefirst intermediary layer, the at least one first intermediary layercomprising at least one of: a tetragonal (001) material, a tetragonal(110) material, a body-centered cubic (bcc) (100) material, aface-centered cubic (fcc) (100) material, a textured bcc (100) material,a textured fcc (100) material, a textured (100) material, or anamorphous material comprising a covalently bonded carbide, a covalentlybonded oxide, or a covalently bonded nitride, and a bismuth antimony(BiSb) layer stack formed over the buffer layer comprising a BiSb layerhaving a (012) orientation, wherein the BiSb layer stack furthercomprises: a first Bi layer, wherein the BiSb layer is disposed on thefirst Bi layer, and a second Bi layer disposed on the BiSb layer,wherein the first and second Bi layers: each has a thickness greaterthan about 0 Å and less than about 10 Å, and sandwich the BiSb layer topromote a (012) BiSb texture and serve as Sb composition modulationslayers configured to improve a chemical uniformity and structure of theBiSb layer degraded by Sb migration.

The buffer layer further comprises an amorphous layer disposed below thefirst intermediary layer, the amorphous layer comprising a materialselected from the group consisting of: NiTa, NiFeTa, NiNb, NiW, NiFeW,NiFeHf, CoHfB, CoZrTa, CoFeB, NiFeB, CoB, FeB, and alloy combinationsthereof with elements selected from the group consisting of: Ni, Fe, Co,Zr, W, Ta, Hf, Ag, Pt, Pd, Si, Ge, Mn, Al, and Ti. The buffer layerfurther comprises at least one second intermediary layer. The at leastone second intermediary layer is a textured bcc (100) material. The atleast one second intermediary layer is a textured fcc (100) material.The SOT MTJ device further comprises an interlayer disposed on the BiSblayer, the interlayer comprising a same material as the at least onefirst intermediary layer. The first and second Bi layers each has awidth of about 0 Å to about 10 Å. The at least one first intermediarylayer comprises the tetragonal (001) or (110) material, the tetragonal(001) or (110) material having an a-axis lattice parameter in the rangeof about 4.18 Å to about 4.75 Å. The at least one first intermediarylayer comprises the fcc (100) material, the fcc (100) material having alattice parameter in the range of about 4.18 Å to about 4.75 Å.

In yet another embodiment, a SOT MTJ device comprises a substrate and abuffer layer formed over the substrate, the buffer layer comprising: atextured layer with a (100) orientation and a first intermediary layerdisposed over the textured layer, the first intermediary layercomprising at least one of a cubic crystal structure selected from thegroup consisting of tetragonal (001), tetragonal (110), body-centeredcubic (bcc) (100), face-centered cubic (fcc) (100), textured bcc (100),and textured fcc (100). The SOT MTJ device further comprises a bismuthantimony (BiSb) layer formed over the buffer layer, the BiSb layerhaving a (012) orientation, wherein the buffer layer is configured toreduce diffusion of Sb in the BiSb layer, and an interlayer disposed onthe BiSb layer.

The buffer layer further comprises an amorphous layer comprising amaterial selected from the group consisting of: NiTa, NiFeTa, NiNb, NiW,NiFeW, NiFeHf, CoHfB, CoZrTa, CoFeB, NiFeB, CoB, FeB, and alloycombinations thereof with elements selected from the group consistingof: Ni, Fe, Co, Zr, W, Ta, Hf, Ag, Pt, Pd, Si, Ge, Mn, Al, and Ti. Theamorphous layer is disposed over the substrate, the textured layer isdisposed on the amorphous layer, the first intermediary layer isdisposed on the textured layer, and the BiSb layer is disposed on thefirst intermediary layer. The buffer layer further comprises one or moresecond intermediary layers, the one or more second intermediary layershaving a cubic crystal structure different than the first intermediarylayer.

The interlayer comprises one or more materials selected from the groupconsisting of: a tetragonal (001) material, a tetragonal (110) material,a body-centered cubic (bcc) (100) material, a face-centered cubic (fcc)(100) material, a textured bcc (100) material, a textured fcc (100)material, a textured (100) material, an amorphous material comprising acovalently bonded carbide, a covalently bonded oxide, or a covalentlybonded nitride, an amorphous metallic material, and a layeredcombination of one or more of any of the preceding materials. Thetextured layer is selected from the group consisting of: RuAl and Crdeposited at a temperature of about 250° C. or greater, Cr in heated CrXalloys where X=Ru, Mo, W, or Ti in less than about 10 atomic percent,the CrX alloys being heated to a temperature less than or equal to about200° C., as CrMo_(n) where n is about 20 atomic percent to about 50atomic percent, or in a sandwich of heated Cr/CrMo_(n) orCrMo_(n)/Cr/CrMo_(n) where n is about 20 atomic percent to about 50atomic percent.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device,comprising: a substrate; a buffer layer formed over the substrate, thebuffer layer comprising: an amorphous sublayer comprising a material inan amorphous structure, wherein the material comprises a covalentlybonded carbide, a covalently bonded oxide, or a covalently bondednitride; and a bismuth antimony (BiSb) layer formed over the bufferlayer, the BiSb layer having a (012) orientation, wherein the bufferlayer is configured to reduce migration of Sb in the BiSb layer.
 2. TheSOT MTJ device of claim 1, wherein the buffer layer further comprisesone or more sublayers, each of the one or more sublayers comprising oneor more materials selected from the group consisting of: a tetragonal(001) material, a tetragonal (110) material, a body-centered cubic (bcc)(100) material, a face-centered cubic (fcc) (100) material, a texturedbcc (100) material, a textured fcc (100) material, a textured (100)material, an amorphous metallic material, and a layered combination ofone or more of any of the preceding materials.
 3. The SOT MTJ device ofclaim 2, wherein at least one sublayer of the one or more sublayerscomprises the bcc (100) material, the bcc (100) material being selectedfrom the group consisting of: V, Nb, Mo, W, Ta, WTi₅₀, Al₁₀Nb₄₀Ti₅₀, Cr,CrMo, CrX where X=Ti, W, Mo, Ru, or RuAl in a B2 phase, and alloycombinations thereof with elements selected from the group consistingof: Ti, Al, Rh, Pd, Pt, Ni, Fe, and Cr.
 4. The SOT MTJ device of claim2, wherein at least one sublayer of the one or more sublayers comprisesthe fcc (100) material, the fcc (100) material being selected from thegroup consisting of: FeO, CoO, ZrO, MgO, TiO, ScN, TiN, NbN, ZrN, HfN,TaN, ScC, TiC, NbC, ZrC, HfC, TaC, WC, CoO, SIC, GaN, FeN, ZnO, MoZr₁₀,MoNi₂₀, NbZr₂₀, and composite combinations thereof with one or moreelements selected from the group of: W, Al, and Si.
 5. The SOT MTJdevice of claim 2, wherein at least one sublayer of the one or moresublayers comprises the tetragonal (001) or (110) material, thetetragonal (001) or (110) material being selected from the groupconsisting of: SbO₂, TiO₂, IrO₂, RuO₂, CrO₂, VO₂, OsO₂, RhO₂, PdO₂,WVO₄, CrNbO₄, SnO₂, GeO₂, ZnNbTi, ZnTiTa, composites thereof, and alloysthereof with elements selected from the group consisting of: W, Ta, andNb.
 6. The SOT MTJ device of claim 5, wherein the tetragonal (001) or(110) material has an a-axis in the range of about 4.49 Å to about 4.69Å and a c-axis in the range of about 2.88 Å to about 3.15 Å.
 7. The SOTMTJ device of claim 2, wherein at least one sublayer of the one or moresublayers comprises the amorphous metallic material, the amorphousmetallic material being selected from the group consisting of: NiTa,NiFeTa, NiNb, NiW, NiFeW, NiFeHf, CoHfB, CoZrTa, CoFeB, NiFeB, CoB, FeB,and alloy combinations thereof with elements selected from the groupconsisting of: Ni, Fe, Co, Zr, W, Ta, Hf, Ag, Pt, Pd, Si, Ge, Mn, Al,and Ti.
 8. The SOT MTJ device of claim 1, wherein the material in theamorphous structure has a nearest neighbor XRD diffraction peak withd-spacing equal to about 2.0 Å to about 2.2 Å, corresponding to a (111)d-spacing from a_(fcc) crystal structure where is a_(fcc) between about3.5 Å and 3.8 Å.
 9. The SOT MTJ device of claim 8, wherein the nearestneighbor distance is about 2.0 Å to about 2.2 Å.
 10. The SOT MTJ deviceof claim 1, further comprising an interlayer disposed on the BiSb layer,the interlayer comprising one or more materials selected from the groupconsisting of: a tetragonal (001) material, a tetragonal (110) material,a body-centered cubic (bcc) (100) material, a face-centered cubic (fcc)(100) material, a textured bcc (100) material, a textured fcc (100)material, a textured (100) material, an amorphous material comprisingcovalently bonded carbide, oxide, or nitride, an amorphous metallicmaterial, and a layered combination of one or more of any of thepreceding materials.
 11. A magnetic recording head comprising the SOTMTJ of claim
 1. 12. A magnetic recording device comprising the magneticrecording head of claim
 11. 13. A magneto-resistive memory comprisingthe SOT MTJ of claim
 1. 14. A spin-orbit torque (SOT) magnetic tunneljunction (MTJ) device, comprising: a substrate; a buffer layer formed onthe substrate, the buffer layer comprising: at least one firstintermediary layer, the at least one first intermediary layer comprisingat least one of: a tetragonal (001) material, a tetragonal (110)material, a body-centered cubic (bcc) (100) material, a face-centeredcubic (fcc) (100) material, a textured bcc (100) material, a texturedfcc (100) material, a textured (100) material, or an amorphous materialcomprising a covalently bonded carbide, a covalently bonded oxide, or acovalently bonded nitride; and a bismuth antimony (BiSb) layer stackformed over the buffer layer comprising a BiSb layer having a (012)orientation, wherein the BiSb layer stack further comprises: a first Bilayer, wherein the BiSb layer is disposed on the first Bi layer, and asecond Bi layer disposed on the BiSb layer, wherein the first and secondBi layers: each has a thickness greater than about 0 Å and less thanabout 10 Å, and sandwich the BiSb layer to promote a (012) BiSb textureand serve as Sb composition modulations layers configured to improve achemical uniformity and structure of the BiSb layer degraded by Sbmigration.
 15. The SOT MTJ device of claim 14, wherein the buffer layerfurther comprises an amorphous layer disposed below the firstintermediary layer, the amorphous layer comprising a material selectedfrom the group consisting of: NiTa, NiFeTa, NiNb, NiW, NiFeW, NiFeHf,CoHfB, CoZrTa, CoFeB, NiFeB, CoB, FeB, and alloy combinations thereofwith elements selected from the group consisting of: Ni, Fe, Co, Zr, W,Ta, Hf, Ag, Pt, Pd, Si, Ge, Mn, Al, and Ti.
 16. The SOT MTJ device ofclaim 15, wherein the buffer layer further comprises at least one secondintermediary layer.
 17. The SOT MTJ device of claim 16, wherein the atleast one second intermediary layer is a textured bcc (100) material.18. The SOT MTJ device of claim 16, wherein the at least one secondintermediary layer is a textured fcc (100) material.
 19. The SOT MTJdevice of claim 14, further comprising an interlayer disposed on theBiSb layer, the interlayer comprising a same material as the at leastone first intermediary layer.
 20. The SOT MTJ device of claim 14,wherein the first and second Bi layers each has a width of about 0 Å toabout 10 Å.
 21. The SOT MTJ device of claim 14, wherein the at least onefirst intermediary layer comprises the tetragonal (001) or (110)material, the tetragonal (001) or (110) material having an a-axislattice parameter in the range of about 4.18 Å to about 4.75 Å.
 22. TheSOT MTJ device of claim 14, wherein the at least one first intermediarylayer comprises the fcc (100) material, the fcc (100) material having alattice parameter in the range of about 4.18 Å to about 4.75 Å.
 23. Amagnetic recording head comprising the SOT MTJ of claim
 14. 24. Amagnetic recording device comprising the magnetic recording head ofclaim
 23. 25. A magneto-resistive memory comprising the SOT MTJ of claim14.
 26. A spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device,comprising: a substrate; a buffer layer formed over the substrate, thebuffer layer comprising: a textured layer with a (100) orientation; anda first intermediary layer disposed over the textured layer, the firstintermediary layer comprising at least one of a cubic crystal structureselected from the group consisting of tetragonal (001), tetragonal(110), body-centered cubic (bcc) (100), face-centered cubic (fcc) (100),textured bcc (100), and textured fcc (100); a bismuth antimony (BiSb)layer formed over the buffer layer, the BiSb layer having a (012)orientation, wherein the buffer layer is configured to reduce diffusionof Sb in the BiSb layer; and an interlayer disposed on the BiSb layer.27. The SOT MTJ device of claim 26, wherein the buffer layer furthercomprises an amorphous layer comprising a material selected from thegroup consisting of: NiTa, NiFeTa, NiNb, NiW, NiFeW, NiFeHf, CoHfB,CoZrTa, CoFeB, NiFeB, CoB, FeB, and alloy combinations thereof withelements selected from the group consisting of: Ni, Fe, Co, Zr, W, Ta,Hf, Ag, Pt, Pd, Si, Ge, Mn, Al, and Ti.
 28. The SOT MTJ device of claim27, wherein the amorphous layer is disposed over the substrate, thetextured layer is disposed on the amorphous layer, the firstintermediary layer is disposed on the textured layer, and the BiSb layeris disposed on the first intermediary layer.
 29. The SOT MTJ device ofclaim 26, wherein the buffer layer further comprises one or more secondintermediary layers, the one or more second intermediary layers having acubic crystal structure different than the first intermediary layer. 30.The SOT MTJ device of claim 26, wherein the interlayer comprises one ormore materials selected from the group consisting of: a tetragonal (001)material, a tetragonal (110) material, a body-centered cubic (bcc) (100)material, a face-centered cubic (fcc) (100) material, a textured bcc(100) material, a textured fcc (100) material, a textured (100)material, an amorphous material comprising a covalently bonded carbide,a covalently bonded oxide, or a covalently bonded nitride, an amorphousmetallic material, and a layered combination of one or more of any ofthe preceding materials.
 31. The SOT MTJ device of claim 26, wherein thetextured layer is selected from the group consisting of: RuAl, and Cr:deposited at a temperature of about 250° C. or greater, in heated CrXalloys where X=Ru, Mo, W, or Ti in less than about 10 atomic percent,the CrX alloys being heated to a temperature less than or equal to about200° C., as CrMo_(n) where n is about 20 atomic percent to about 50atomic percent, or in a sandwich of heated Cr/CrMo_(n) orCrMo_(n)/Cr/CrMo_(n) where n is about 20 atomic percent to about 50atomic percent.
 32. The SOT MTJ device of claim 26, wherein the firstintermediary layer comprises the tetragonal (001) or (110) material, thetetragonal (001) or (110) material being ruthenium (IV) oxide (RuO₂).33. A magnetic recording head comprising the SOT MTJ of claim
 26. 34. Amagnetic recording device comprising the magnetic recording head ofclaim
 33. 35. A magneto-resistive memory comprising the SOT MTJ of claim26.